Ecosystem Dynamics: Natural vs. Artificial Changes
Changes in Natural Ecosystems
Ecosystems are dynamic structures that vary over time, tending towards an equilibrium state with minimal change. For an ecosystem to be in equilibrium, at least two conditions must be met:
- Environmental factors must remain stable.
- The number of individuals in the population should remain relatively constant.
The state of equilibrium in an ecosystem is an ideal, as all ecosystems are subject to internal and external changes.
These changes may be due to various causes and have different durations. They can be:
- Natural: Originating from the internal dynamics of the ecosystem.
- Artificial: Resulting from anthropogenic activity (human impact on the environment).
Depending on their duration, the changes can be:
- Gradual: Occurring slowly over long periods.
- Catastrophic: Happening quickly in a short period.
Natural transformations affecting the biotope occur gradually over geological time, spanning thousands of years. These affect the topography, soil, climate, etc. The biotope can also change suddenly and catastrophically, for example, due to a volcanic eruption or an earthquake.
Natural changes affecting biocenosis usually occur over hundreds of years, within biological time.
Changes due to human activity occur in social time, a short interval that can be several years or decades. Logging or burning a forest are examples of anthropogenic transformations.
Global Changes
Throughout Earth’s history, there have been sudden changes in environmental conditions that, in one way or another, affect the entire planet.
Glacial ice covering large areas of land is one example. These prolonged periods of global cooling affected ecosystems worldwide. Many species disappeared, and the distribution of many others was altered.
About 65 million years ago, another dramatic change led to the demise of the dinosaurs and many species of plants and animals. The most accepted explanation for this mass extinction is the impact of a meteorite.
Rhythmic Changes in Ecosystems
All ecosystems experience cyclical and predictable changes that can be observed directly. These changes are due to Earth’s dynamics and the movements of the sun, Earth, and moon.
The alternation of day and night and the cycle of tidal changes are short cycles that affect living things.
The Alternation of Day and Night
This affects all ecosystems directly, except in some where there is no light, such as caves and the seabed.
During the day, photosynthesis predominates over respiration. In marine ecosystems, for example, there are vertical migrations of phytoplankton in the water column. During the day, photosynthetic organisms are located close to the surface, and at night, they move away from it.
In terrestrial ecosystems, animals can be active during the day or night, distinguishing between diurnal and nocturnal animals. Each uses this activity for food. This alternation in activity increases the niche and, therefore, diversity in ecosystems.
The Alternation of Seasons
This affects all ecosystems, especially those in temperate zones, where living beings are adapted to the cyclical changes that occur throughout the year, such as changes in the hours and intensity of light, temperature, and rainfall.
Seasonality also determines the time of reproduction for many creatures. Plants flower when a certain number of daylight hours are reached, and most animals have annual rhythms of reproduction to ensure that offspring are born during periods favorable for development.